Synchronized feature patterns of local field potentials in hippocampal-prefrontal cortex during working memory based on time-varying spectral coherence / 国际生物医学工程杂志

Objective:To investigate the synchronized feature patterns of local field potentials in the hippocampus (HPC) and prefrontal cortex (PFC) during working memory based on time-varying spectral coherence so as to support the study of information processing mechanisms in working memory.Methods:The local field potentials (LFPs) signals of the ventral hippocampus (vHPC) and medial prefrontal cortex (mPFC) were collected from six SD rats during the performance of a spatial working memory task in the Y-maze, and the time-frequency distributions of vHPC and mPFC LFPs were calculated by applying the short-time Fourier transform (STFT) to determine the characteristic frequency bands of the working memory and then to investigate the synchronized patterns of vHPC and mPFC LFPs based on the coherent of the time-varying frequency spectrum. Finally, support vector machines were applied to explore the feasibility of applying spectral coherence values to predict working memory.Results:When rats performed working memory tasks correctly, the energy of the theta band (4 - 12 Hz) of the HPC and PFC increased (all P < 0.01), and the spectral coherence value of the theta band of the HPC-PFC increased ( P < 0.05). Support vector machine training and prediction using the average peak spectral coherence and the difference between the peak and the onset when correctly and incorrectly executing the working memory as features resulted in 89% accuracy, 90% precision, 88% recall, and 88% F1 scores, all of which were statistically significant differences compared to the results of the randomly disrupted labeled data rearranging (all P < 0.05). Conclusions:Synchronized synergy in the HPC-PFC theta band is one of the potential mechanisms for correctly performing information processing in working memory.

Connectivity pattern of action potentials causal network in prefrontal cortex during anxiety / 生物医学工程学杂志

Anxiety disorder is a common emotional handicap, which seriously affects the normal life of patients and endangers their physical and mental health. The prefrontal cortex is a key brain region which is responsible for anxiety. Action potential and behavioral data of rats in the elevated plus maze (EPM) during anxiety (an innate anxiety paradigm) can be obtained simultaneously by using the and in conscious animal multi-channel microelectrode array recording technique. Based on maximum likelihood estimation (MLE), the action potential causal network was established, network connectivity strength and global efficiency were calculated, and action potential causal network connectivity pattern of the medial prefrontal cortex was quantitatively characterized. We found that the entries (44.13±6.99) and residence period (439.76±50.43) s of rats in the closed arm of the elevated plus maze were obviously higher than those in the open arm [16.50±3.25, <0.001; (160.23±48.22) s, <0.001], respectively. The action potential causal network connectivity strength (0.017 3±0.003 6) and the global efficiency (0.044 2±0.012 8) in the closed arm were both higher than those in the open arm (0.010 4±0.003 2, <0.01; 0.034 8±0.011 4, <0.001), respectively. The results suggest that the changes of action potential causal network in the medial prefrontal cortex are related to anxiety state. These data could provide support for the study of the brain network mechanism in prefrontal cortex during anxiety.

LFPs coding working memory task via information entropy using plugin method / 国际生物医学工程杂志

Objective Toinvestigatetheentropyoflocalfieldpotentials(LFPs)recordedinratmedialprefrontal cortex during a Y-maze working memory (WM) task, to provide computing support for neural coding mechanism.Methods Sixteen-channel LFPs were recorded from SD rats while they performed a Y-maze WM task.The data came from 4 rats, 20 trials (10 correct trials and 10 incorrect trials) per rat provided by laboratory of neurobiology in medicine,Tianjin Medical University.Original LFPs were preprocessed to remove 50 Hz power line noise and baseline drift.Multi-taper Fourier transform was applied to calculate spatial distributions of LFPs and band pass filter were used to extract characteristic signal.The entroy coding of 16 channel LFPs was as follows: the physiological window was set to be 500 ms, the step length of physiological window was set to be 125 ms, windows were added to LFPs data, and then LFPs entropy of each sliding window was computed and averaged to get the trend of multichannel entropy values duringthe WM task.Results The power of θ band (4-12 Hz) in LFPs increased.The averaged entropy value ofmultichannel θ band LFPs in correct trials was 0.939±-0.020, which were larger than those in the resting state, 0.795±0.031 (P＜0.05).Those during wrong WM task had no significant difference, which didn't encode the WM task.Conclusions The principal frequency band related to WM is the θ band and LFPs entropy encodes the WM effectively.

Determination of contact angle of pharmaceutical excipients and regulating effect of surfactants on their wettability / 药学学报

To study the effects of surfactants on wettability of excipients, the contact angles of six types of surfactants on the surface of two common excipients and mixture of three surfactants with excipients were measured using hypsometry method. The results demonstrated that contact angle of water on the surface of excipients was associated with hydrophilcity of excipients. Contact angle was lowered with increase in hydrophilic groups of excipient molecules. The sequence of contact angle from small to large was starch < sodium benzoate < polyvinylpyrrolidone < sodium carboxymethylcellulose < sodium alginate < chitosan < hydroxypropyl methyl cellulose

Characteristic pattern of neuron firings at hippocampus CA1 for fast-aging mouse / 国际生物医学工程杂志

Objective To investigate the effect of fast-aging on the excitability of hippocampus CA1 neurons in mouse and the possible interaction between fast-aging and hippocampus. Methods Using brain slice and extracellular recording technique to record the firing of hippocampus CA1 neurons in fast-aging(SA M-P/8) and normal control mice, after preprocessing, neural firing train were obtained. Using neural firing rate and inter-spike-inter to investigate interaction between fast-aging and hippocampal neural firing. Results The neural firing rate of hippocampus CA1 neurons in fast-aging mice is (1.052±0.364) Hz(n=14), while the neural firing ratein normal control mice is (4.416±1.306) Hz(n=22). In fast-aging mice, 80.5% inter spike intervel(ISI) is longerthan 1sec, but in normal control mice, 95.6% ISI is shorter than 0.5sec. Conclusion The decreased firing rate of hippocampus CA1 and longer ISI observed in the fast-aging mice indicates that fast-aging significantly inhibit hippocampal CA1 neurons excitability.